Häcker, A-L, Bigras, J-L, Henderson, M, Barnett, TA, and Mathieu, M-E. Motor skills of children and adolescents with obesity and severe obesity-a CIRCUIT study. J Strength Cond Res 34(12): 3577-3586, 2020-During childhood, excessive weight is negatively associated with the development of motor skills, with overweight children or children with obesity having poorer motor skills compared with children with normal weight. The objectives of the current study are to identify the differences in motor skills between children and adolescents with obesity and severe obesity and the extent of this difference. To do so, we examined cross-sectionally 165 subjects. Physical fitness was analyzed in both subjects with obesity (>97th to 99.9th body mass index [BMI] percentile) and severe obesity (>99.9th BMI percentile) using 8 standardized tests: sit-and-reach, grip force, sit-ups, push-ups, balance, hand-eye coordination, standing long jump and 5-m shuttle run. Poorer performance were observed in subjects with severe obesity in sit-ups (children: 59%; 18.6 ± 17.0 vs. 29.5 ± 23.2 percentile value, p = 0.008), balance (adolescent: 59%; 12.1 ± 12.2 vs. 19.3 ± 13.9 seconds, p = 0.034), and in the 5-m shuttle run (children: 49%; 14.0 ± 13.9 vs. 20.8 ± 19.4 percentile value, p = 0.046; adolescents: 11%; 13.2 ± 2.2 vs. 11.8 ± 1.6 seconds, p = 0.008) compared with obese counterparts. In conclusion, although physical performance was found to be similar between the different obesity levels for most tests, youth with severe obesity demonstrated impairments ranging from 11 to 59% in specific tests.